Since the Freon-based refrigerants have been subject to the chlorofluorocarbon control, an HFC-based refrigerant has become used as an alternative refrigerant. This HFC-based refrigerant contains no chlorine atom in the molecular structure thereof, and therefore, the lubrication performance of the compressor is reduced. Moreover, the HFC-based refrigerant, which structurally has a strong polarity, has the properties that it dissolves neither nonpolar sludge nor contaminant (mineral oil and the like) and tends to easily precipitate them in the condensed liquid refrigerant. The precipitate adheres to the cramped portions of a capillary tube, an expansion valve and the like, causing clogging. This consequently causes abnormal stop due to the discharge temperature rise of the compressor and the compressor failure due to the malfunction of the expansion valve, and therefore, it is required to devise sufficient countermeasures.
Moreover, the synthetic oil of ether oil, ester oil or the like is employed as a refrigerating machine oil for this HFC-based refrigerant since mutual solubility with the refrigerant becomes one of important characteristics. However, the synthetic oil, which has a strong polarity, therefore has the property that it easily dissolves the residual impurities other than the refrigerating machine oil and the refrigerant. Therefore, in a refrigeration apparatus that employs a synthetic oil as a refrigerating machine oil, clogging with sludge and the like after the evaporation of the refrigerant tends to easily occur in a decompression mechanism constructed of an electric expansion valve, and this easily causes a problem that abnormality occurs in the refrigeration cycle.
It is often the case where the refrigerant piping is laid in walls in apartment houses and buildings. In the case where the refrigerant piping is laid in walls as described above, the existence of the contaminants of the residual refrigerating machine oil and so on in the existing interconnecting piping emerges as a problem when installing a new air conditioner by removing the existing air conditioner. Particularly when the HFC-based refrigerant is employed as described above, it is required to remove the residual contaminants in this existing interconnecting piping as much as possible. Accordingly, there has been the conventional practice of removing the existing air conditioner, thereafter cleaning the existing interconnecting piping to remove the contaminants including the residual refrigerating machine oil for the securing of cleanliness and thereafter installing a new air conditioner.
However, the conventional method of cleaning the existing interconnecting piping, as described above, has a problem that it needs much labor and time and needs a considerable amount of cost for the installation of a new air conditioner.